Porsche 928

The next phase of my interior restoration is to fix up the arm rests on the doors, so I thought I would relate my progress to the list.

If you have ever removed your shark's door lining to do some speaker work, or window rail and runner replacement then you will know that all that holds the arm rests on are five large bolts that go through the plastic moulding of the arm rest, the fibre board of the liner and into the metal of the door.

The result is that each time you close the door you are pulling on the plastic of the arm rest. Over the years the plastic hardens and will begin to crack and break off around the bolts. My drivers side door was down to one bolt holding the arm rest on. All the mount points of the rest were broken clean off.

The passenger side felt good, however I checked it just in case, and discovered that the plastic was already cracked and broken in places. So if you have a shark built earlier than the 90's I would pop out the trim panel in the center of each door and just take a peak. It will be easy to see if there are problems developing. If you get it early its much easier to fix. If not then you are up for a new arm rest (if you can get one) or a big repair job.

I have opted to repair mine as the skin on it is still in good shape. If anyone else is in the same boat as me then I am happy to lend you the moulds that I am making up for fibre glass repair.

So far I have replaced all the missing plastic for the two bolt holes on the rear end of the arm rest as well as reinforcing the remaining plastic so that the problem won't occur again. Next comes the three major hangers in the middle of the arm rest, two on the top and one on the bottom. They should be no more difficult than the first set, once I construct the moulds for them.

During the week I finished the moulds for the end bolt holes. They are made from 3mm craft wood and are held on to the arm rest using a nut and bolt through a hole drilled through the mould back and a part of the arm rest that is out of view behind the centre trim panel.

The design works well and gives a nice neat fit. The hard surface of Kraft Wood makes for a good finish. Candle wax served well as a mould release agent, but you have to make sure the coverage is complete and not to scratch the wax when you are setting up and applying the resin.

I didn't bother with gel coat colouring as the re-built sections will be hidden. So colouring the resin seemed excessive.

The new corners have been cast and the result was good. Nice clean release of the moulds and a new chunk of plastic that matched the thickness of the original.

The result: One very strong rigid repair. The epoxy resin and glass will be a lot stronger and less likely to crack than the original. I much prefer epoxy resin in this application as its less brittle than polyester resin. So the repair should last a lot longer.

A small section of the general glass layer will be visible inside the pocket on the arm rest, but only if you look hard. I think that it is a worthwhile trade off a strong repair that will last "for ever".

In the above image you are looking at the repaired rear end of the driver's side arm rest and the mold used to do the job. The off white area on the top corner is the repair itself, you can see how it was formed by the mold.

The second mold is easier to build, requiring only two layers of Kraft Wood. Note the hole in the mold on the left side used for bolting the mold onto the arm rest. It is a bit larger than required. This is useful as it allows accurate alignment of the mould when attaching. This is not necessarily easy to do when drilling the hole. A large washer under the nut stops the nut from pulling through the hole.

And shown in place. Note: The mold was made out of a few scraps that I had lying around, hence it is much larger than it actually needs to be.

This is the final product. You will note that I have added some more layers of 4 ounce fibre glass cloth over the top of the whole area. This was done on both sides to sandwich the repaired areas in and give strength to the whole repair. The results are exceptionally strong and I hope they will last the rest of the car's life time.

Here we have the bottom tab on the arm rest. As you can see from the colour it had to be completely rebuilt. Because there was no easy way to attach a mould, I simple sat the arm rest down on its mounting side on a piece of plastic wrap and applied one layer of fibre glass and resin to the inside edge, that extended out where the original plastic had been. Once that had cured, I used a Dremel grinding wheel to shape the glass so that it looked like the original. More layers were then built up on top and the other side to get the right thickness and hold it in place.

The repair of the main mounting points was a tricky job. I tried constructing a mould, but had no luck. The original plastic was badly broken, so I glued the pieces back in to act as a guide. Acetone is good for this, it will melt the plastic nicely. Paint it on both pieces to be joined then press them together. The join isn't strong, but good enough to serve as a base to glass over.

To replace the missing plastic I applied a piece of glass cloth and resin over the back of the broken area, that protruded out past the edges. Because of the stepped shape of the plastic, the fibre glass was held in shape as the resin cured. Once the first layer had dried I applied a few more to this "scaffold" and allowed that to cure. It was then easy enough to shape the glass using the Dremel, so that it matched the original plastic that was missing.

You can also see that I extended more layers of fibre glass right down and around the bottom of the arm rest. The aim of this was to spread the load imposed on the repaired areas around as much as possible.

Looking from the other side you can see that I also ran the fibre glass over the front side as well. The aim was to sandwich the repairs in and increase their strength. The results seem quite strong.